1. Technical Field of the Invention
This invention relates to semiconductor wafer manufacturing, and more particularly, to a stackable cassette used in the processing of semiconductor wafers.
2. Description of Related Art
During the manufacture and processing of semiconductor wafers, cassettes are utilized to store and transport the wafers. These cassettes provide a protection for the wafers. A cassette holds several wafers, the standard cassette holds 13 or 25 wafers. The wafers are normally stacked horizontally, one above the other, which prevents each wafer from touching any other wafer. During the processing of these wafers, it is necessary for the manufacturer to occasionally monitor or test the results of different recipes used in the manufacturing of the wafers. Manufacturers refer to these wafers as test wafers and have used several methods to manufacture the test wafers. In one method, the manufacturer stops the processing of an entire cassette of wafers during a test cycle. However, this method is very time consuming, since it results in the stopping and starting of the wafer processing. This may result in a large economic penalty for a manufacturer.
In another method of testing wafers during their processing, manufacturers process a single wafer in the cassette. But this method suffers from the disadvantage of wasting the time necessary to process one wafer individually when several wafers could be processed during the same time period.
Manufacturers sometimes process an entire cassette of wafers and then test for the quality of the wafers. But manufacturers run the costly risk of processing an entire cassette of defective wafers. Additionally, in all of these methods, the manufacturer loses an efficient use of their processing operators, disrupting the flow of the wafer processing.
In the past, wafer cassettes have been known to be stackable for storage. However, these stackable cassettes do not allow the processed wafers to be directly placed within the stackable cassettes from the processing chamber.
Thus, it would be a distinct advantage to have an apparatus, system, and method providing the efficient testing of wafers during the processing of semiconductor wafers. It is an object of the present invention to provide such an apparatus, system, and method.